Description

Nori Human Cystatin C ELISA Kit Summary

Alternative names for cystatin C: cystatin 3, CST3, gamma trace, post-gamma-globulin, or neuroendocrine basic polypeptide

Standard Curve

Kit Components
1. Pre-coated 96-well Microplate
2. Biotinylated Detection Antibody
3. Streptavidin-HRP Conjugate
4. Lyophilized Standards
5. TMB One-Step Substrate
6. Stop Solution
7. 20 x PBS
8. Assay Buffer

Other Materials Required but not Provided:
1. Microplate Reader capable of measuring absorption at 450 nm
2. Log-log graph paper or computer and software for ELISA data analysis
3. Precision pipettes (1-1000 µl)
4. Multi-channel pipettes (300 µl)
5. Distilled or deionized water

Protocol Outline
1. Prepare all reagents, samples and standards as instructed in the datasheet.
2. Add 100 µl of Standard or samples to each well and incubate 1 h at RT.
3. Add 100 µl of Working Detection Antibody to each well and incubate 1 h at RT.
4. Add 100 µl of Working Streptavidin-HRP to each well and incubate 20 min at RT.
5. Add 100 µl of Substrate to each well and incubate 5-30 min at RT.
6. Add 50 µl of Stop Solution to each well and read at 450 nm immediately.

Background:

Cystatin C or cystatin 3 (formerly gamma trace, post-gamma-globulin, or neuroendocrine basic polypeptide), a protein encoded by the CST3 gene, is mainly used as a biomarker of kidney function. Cystatin C belongs to the type 2 cystatin gene family and has a low molecular weight (13.3 kilodaltons). Recently, it has been studied for its role in predicting new-onset or deteriorating cardiovascular disease. It also seems to play a role in brain disorders involving amyloid, such as Alzheimer’s disease. In humans, all cells with a nucleus produce cystatin C as a chain of 120 amino acids. It is found in virtually all tissues and body fluids. It is a potent inhibitor of lysosomal proteinases and probably one of the most important extracellular inhibitors of cysteine proteases. Cystatin C is removed from the bloodstream by glomerular filtration in the kidneys. If kidney function and glomerular filtration rate decline, the blood levels of cystatin C rise. Cross-sectional studies suggest that serum levels of cystatin C are a more precise test of kidney function than serum creatinine levels.^[1] Cystatin C levels are less dependent on age, gender, ethnicity and muscle mass compared to creatinine. Cystatin C measurements alone have not been shown to be superior to formula-adjusted estimations of kidney function.^[2] As opposed to previous claims, cystatin C has been found to be influenced by body composition.^[3] It has been suggested that cystatin C might predict the risk of developing chronic kidney disease, thereby signaling a state of ‘preclinical’ kidney dysfunction.^[4] Cystatin C levels have been reported to be altered in patients with cancer,^[5] (even subtle) thyroid dysfunction^[6] and glucocorticoid therapy in some^[7] but not all^[1] situations. The levels may be influenced by cigarette smoking and levels of C-reactive protein^[8] and seem to be increased in HIV infection, which might or might not reflect actual renal dysfunction.^[9] The role of cystatin C to monitor GFR during pregnancy remains controversial. Like creatinine, the elimination of cystatin C via routes other than the kidney increase with worsening GFR. Cystatin C levels are decreased in atherosclerotic and aneurysmal lesions of the aorta^[10], but increased levels may be associated with the risk of death.

References

1. Roos JF, et al. (2007). Clin. Biochem. 40 (5–6): 383–391.
2. Stevens LA, et al. (2008). Am. J. Kidney Dis. 51 (3): 395–406.
3. Shlipak MG (2007). Nat Clin Pract Nephrol. 3 (4): 188–189.
4. Shlipak MG, et al. (2006). Annals of Internal Medicine. 145 (4): 237–46.
5. Demirtaş S, et al. (2006). Clin. Biochem. 39 (2): 115–118.
6. Fricker M, et al. (2003). Kidney Int. 63 (5): 1944–1947.
7. Risch L, et al. (2001). Clin. Chem. 47 (11): 2055–9.
8. Knight EL, et al. (2004). Kidney Int. 65 (4): 1416–1421.
9. Odden MC, et al. (2007). Arch. Intern. Med. 167 (20): 2213–2219.
10. Shi GP, et al. (1999). J. Clin. Invest. 104 (9): 1191–1197.

Product Citation

40.